flu

noun

ˈflü 

1

: influenza

2

: any of several virus diseases marked especially by respiratory or intestinal symptoms

flu-like

ˈflü-ˌlīk 

adjective

Examples of flu in a Sentence

He came down with a bad bout of the flu.

Recent Examples on the Web

The state requires vaccination for only a relatively small number of infections, Siri wrote in an email to CNN, but there are hundreds of other pathogens that either don’t have vaccines or aren’t required for school attendance, like Covid-19 or the flu. —Brenda Goodman, CNN Money, 5 Sep. 2025

Experts say a balanced diet, good sleep, and stress management are still the best ways to fight colds and flu. —Maggie O'Neill, Verywell Health, 4 Sep. 2025

And recent outbreaks of the avian flu have killed off millions of waterfowl and shorebirds. —Sophie Hartley, IndyStar, 3 Sep. 2025

This innovative platform, which researchers are exploring for applications ranging from flu to cancer to AIDS, poses a threat to global defenses against future crises and hinders progress in biomedical innovation. —Bernadette Boden Albala, Forbes.com, 3 Sep. 2025

Word History

Etymology

by shortening

First Known Use

1839, in the meaning defined at sense 1

Phrases Containing flu

• anti-flu
• Asian flu
• bird flu
• blue flu
• flu season
• swine flu
• yuppie flu

Rhymes for flu

• blew
• blue
• boo
• brew
• chew
• chou
• clue
• coo
• coup
• crew
• cue
• dew

Kids Definition

flu

noun

ˈflü 

1

: influenza sense 1

2

: any of several virus diseases that are something like a cold

flu-like

ˈflü-ˌlīk

adjective

Medical Definition

flu

noun

ˈflü 

1

: influenza

2

: any of several chiefly viral illnesses marked especially by respiratory or gastrointestinal symptoms see intestinal flu

flu-like

-ˌlīk 

adjective

also flulike

flu-like symptoms